In order to ensure strong adhesion of parts in a structure, it is important to apply sufficient adhesive to the adhesive faces. Accordingly, most often a certain amount of excess adhesive flows out from all sides of the adhesive joint when the parts are pressed towards each other. Large tolerances on the constituent elements and hence comparatively large variations in the final size of the adhesive joint also contribute to making it difficult to determine the requisite and sufficient amount of adhesive for obtaining a strong joint, which is solved in the simplest and most expedient way by applying adhesive abundantly. Usually the out-flowing adhesive is removed and the adhesive joint is smoothened both for aesthetic considerations and often also for various functional considerations. This can be done either by simply scraping or wiping off the adhesive prior to it having set completely or by removing it mechanically, eg by sanding.
When joining completely or partially closed structures or structures with particular geometries by adhesion, however, it may be difficult or even impossible to remove excess adhesive pressed out of the joint. This is the case eg for blades for wind turbines that consist of blade shells that are adhered to each other with internal bracing beams. Here the excess adhesive is on the inside of the blade in large “burrs”. Unless they are removed, they will, once the blade is taken into use, to some extent brake off and rattle around interiorly of the blade. This is undesirable in itself as it entails generation of much noise to the nuisance of the environment surrounding the wind turbine. Over time, the adhesive lumps are pulverised by being thrown around, but they are then found to connect with humidity and water penetrating into the blade and form large lumps that, on the one hand, clog drainage openings and, on the other, impart severe impact forces on the interior parts of the blade during rotation of the blade.
In order to avoid this, it is therefore desirable to remove the excess adhesive pressed out of the adhesive joints when the blade is assembled. This can be done manually some distance into the blade, which is, however, on the one hand a labour- and time-intensive process and, on the other, it is not ideal for working environment considerations. Alternatively, so-called adhesive traps, looking like long narrow gutters, can be mounted inside the blade into which the adhesive runs during the assembly, and which are optionally subsequently pulled out of the blade. However, this is a cumbersome and time-intensive process.
In DK 175718 the interior bracing beam is combined from two beam parts which enables height adjustment of the overall height of the beam, thereby to a certain degree enabling compensation for dimensional inaccuracies on the blade shells. However, the beam parts still need to be adhered to each other and therefore there are, also in that case, problems associated with excess adhesive from the adhesive joints. In the disclosure the so-called joining panels are used that are mounted on the body parts extending across the joining surface, but with a slot there between into which a part of the excess adhesive may then flow. This method corresponds to the use of the above-mentioned adhesive traps and is associated with the same drawbacks.
It is known eg from WO 03046394 to avoid burrs of out-flowing adhesive by providing particular configurations of the adhesive faces of the one or both structural parts, into which excess adhesive may flow. However, this presupposes a mechanical processing of the joining faces, which considerably increases the costs of the adhesion process. Moreover, such grooves or cutouts will be able to take up only a certain amount of adhesive, and hence out-flowing adhesive cannot be entirely obviated if the adhesive joint is to compensate eg for large tolerances and inaccuracies on the constituent parts and ensuing very varying needs for adhesive.